It's a simple Expression Language (EL) for Java, the code base sometime ago was migrated to the Apache commons ognl and this source code is used just to maintenance 3.x branch. The new version from Apache will start from 4.x

Out of incubator and now officially found here http://commons.apache.org/ognl/

• Javassist added back as a dependency WW-3544

• small fix to solve a problem with compiling under JDK5

• small fix to improve performance WW-3580

• Adds possibility to discover eval chain

• partially reverts previous changes to allow OGNL to work in environment with Security Manager enabled WW-3746

• important performance improvement OGNL-224 - thanks to Pelladi Gabor
• race condition fix OGNL-226 - thanks to Johno Crawford

• uses better method to calculate method's cache key WW-4113 - thanks to Kevin Su

• added better capitalization logic for methods WW-3909 - thanks to Iwen.ma